Bacteriorhodopsin (BR) is a small integral membrane protein that functions as a light-driven proton pump. We have grown crystals of bR from the cubic lipid phase. Following a 2.3 A resolution structure determination of the wild type, light-adapted form of bacteriorhodopsin (Luecke et aL, 1998), we have obtained crystals that diffract at 1.5 A resolution. The elucidated structure revealed the locations of functional water molecules as well as the phospholipid bilayer surrounding the BR trimers (manuscript being reviewed at Science). Collection of higher resolution native data would enable us to refine the wild-type structure to higher resolution. Higher resolution maps would also allow us to more confidently place water molecules which are of great importance in the proton translocation pathway. Data collection on BioCARS Station 14-BM-C.